Department of Pediatric Surgery, Shengjing Hospital of China Medical University, Heping District, Shenyang 110004, PR China.
J Pediatr Surg. 2010 Nov;45(11):2195-202. doi: 10.1016/j.jpedsurg.2010.06.020.
BACKGROUND/PURPOSE: The embryogenesis of the internal anal sphincter (IAS) in anorectal malformations (ARMs) remains unclear. This study aimed to investigate the development of the smooth muscle in the terminus of the digestive tract in normal and abnormal rats.
Rat embryos with ARMs were generated by administration of ethylenethiourea to pregnant rats. The normal rat embryos and embryos with ARMs from E13.5 to E21 were serially sectioned in the sagittal plane and stained immunohistochemically using specific antibody to α-smooth muscle actin (SMA). Temporospatial study was carried out on circular muscle of the distal portion of the hindgut.
α-Smooth muscle actin immunolabeling cells could not be observed in the hindgut on E13.5, E14, and E14.5. On E15, there were α-SMA immunolabeling circular muscle cells in the hindgut; and the distal portion of the circular muscle was not thickened in the normal and ARMs rats. From E16 onward, the smooth muscle with slight dilated terminus, which was characterized by the features of IAS, could be noted in the primitive anorectum. In the normal group, the circular muscle in the distal portion of the hindgut thickened slightly and became the musculature with shutter-like bundles. In the ARMs group, the α-SMA immunolabeling myogenic precursors of the smooth muscle could be observed in the primitive anorectum as well. The musculature was similar to that in the normal group. On E15 and E16, there was no significant difference in the development of the circular muscle in the 2 groups. Moreover, the terminus of the circular muscle in the hindgut did not reach the orificium fistulae in ARMs rats. From E17 onward, in ARMs rats, the funnel-shaped distal hindgut communicated the genitourinary tract with a narrow fistula; the dilated musculature at this portion thinned gradually and formed an acute angled extremity in the ARMs group rather than formed blunt extremity in the normal group; the terminus circular muscle in the dorsal hindgut reached the orificium fistulae. During the following gestational days, the circular muscle of the hindgut in both normal and ARMs rats continued its own tendency.
The IAS primordium started to appear at the terminus of the hindgut on E15 in the 2 groups. The IAS in the ARMs group failed to develop as well as that in the normal group. The IAS dysplasia occurred in the late embryonic development (E17-E21).
背景/目的：肛门直肠畸形（ARM）中内肛门括约肌（IAS）的胚胎发生仍不清楚。本研究旨在研究正常和异常大鼠消化道末端平滑肌的发育情况。
通过给怀孕的大鼠施用乙撑硫脲来生成 ARM 大鼠胚胎。对来自 E13.5 至 E21 的正常大鼠胚胎和 ARM 大鼠胚胎进行矢状面连续切片，并使用针对α-平滑肌肌动蛋白（SMA）的特异性抗体进行免疫组织化学染色。对后肠远端的环形肌进行时空研究。
在 E13.5、E14 和 E14.5 时，后肠中观察不到α-平滑肌肌动蛋白免疫标记细胞。在 E15 时，后肠中有α-SMA 免疫标记的环形肌细胞；并且正常和 ARM 大鼠的环形肌远端没有增厚。从 E16 开始，可以在后肠原始肛门口注意到具有轻微扩张末端的平滑肌，其特征为 IAS。在正常组中，后肠远端的环形肌轻微增厚，并成为具有百叶窗状束的肌肉。在 ARM 组中，也可以在后肠原始肛门口观察到平滑肌的α-SMA 免疫标记肌原前体。肌肉结构与正常组相似。在 E15 和 E16 时，两组的环形肌发育没有差异。此外，ARM 大鼠的后肠环形肌末端未到达瘘口。从 E17 开始，在 ARM 大鼠中，漏斗形后肠将泌尿生殖道与狭窄的瘘管相通；该部位扩张的肌肉逐渐变薄，并在 ARM 组中形成锐角，而在正常组中则形成钝角；背侧后肠的环形肌末端到达瘘口。在随后的妊娠天数中，正常和 ARM 大鼠的后肠环形肌继续保持其自身的趋势。
在两组中，IAS 原基均于 E15 时开始出现在后肠末端。ARM 组的 IAS 未能发育，与正常组一样。IAS 发育不良发生在胚胎发育后期（E17-E21）。
